ABSTRACT Support is requested for a Keystone Symposia conference entitled Cancer Immunotherapy: Mechanistic Insights to Improve Clinical Benefit, organized by Drs. Padmanee Sharma, Aviv Regev, Crystal L. Mackall and Kristen Hege. The conference will be held in Whistler, British Columbia from March 10-14, 2019. Cancer immunotherapy is an established field that has led to remarkable clinical benefit for a subset of patients. However, a deeper understanding of the mechanisms of response and resistance to current immunotherapy strategies is needed to help develop new treatments that will increase the number of patients who will benefit. This Keystone Symposia conference is focused on immunotherapy as a treatment for cancer, including potential combination therapies and development of new technologies to elucidate novel targets and/or biomarkers that will be used to design new treatments and enable appropriate patient selection to improve clinical outcomes for cancer patients. The conference will bring together leading and emerging scientists to advance the development of new immune-based treatments for cancer. Discussions will also consider the future directions of the field, including the identification of the most pressing unanswered questions, the areas needing more focus, and those that would benefit from new approaches and methodologies developed and used in other related fields. .